/* JAI-Ext - OpenSource Java Advanced Image Extensions Library
 *    http://www.geo-solutions.it/
 *    Copyright 2018 GeoSolutions
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Copyright (c) 2018, Michael Bedward. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright notice, this
 *   list of conditions and the following disclaimer in the documentation and/or
 *   other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.imagen.media.jiffle.runtime;

import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Simple ThreadFactory implementation to supply daemon threads with specified priority. Used by JAITools classes that
 * run polling services on background threads to avoid blocking application exit.
 *
 * @author Michael Bedward
 * @since 1.1
 * @version $Id$
 */
public class DaemonThreadFactory implements ThreadFactory {

    private static final String DEFAULT_ROOT_NAME = "daemon-";

    private final ReentrantLock lock = new ReentrantLock();
    private static final AtomicInteger threadCount = new AtomicInteger(0);
    private final int priority;
    private final String rootName;

    /** Creates a new factory which will supply daemon threads having normal priority. */
    public DaemonThreadFactory() {
        this(Thread.NORM_PRIORITY, DEFAULT_ROOT_NAME);
    }

    /**
     * Creates a new factory which will supply daemon threads to run at the specified priority.
     *
     * @param priority thread priority
     */
    public DaemonThreadFactory(int priority) {
        this(priority, DEFAULT_ROOT_NAME);
    }

    /**
     * Creates a new factory which will supply daemon threads to run at the specified priority. Threads will be named
     * {@code rootName-n} where {@code n} is the count of threads produced by all instances of this class.
     *
     * @param priority thread priority
     * @param rootName root name to label threads
     */
    public DaemonThreadFactory(int priority, String rootName) {
        String s = rootName == null ? "" : rootName.trim();
        if (s.length() == 0) {
            this.rootName = DEFAULT_ROOT_NAME;
        } else if (s.endsWith("-")) {
            this.rootName = s;
        } else {
            this.rootName = s + "-";
        }

        this.priority = Math.min(Thread.MAX_PRIORITY, Math.max(Thread.MIN_PRIORITY, priority));
    }

    /**
     * Creates a new daemon thread with name and priority assigned as per the values supplied when creating this thread
     * factory.
     *
     * @param r target for the new thread
     * @return new thread
     */
    public Thread newThread(Runnable r) {
        lock.lock();
        try {
            Thread t = new Thread(r);
            t.setDaemon(true);
            t.setName("daemon-" + threadCount.getAndIncrement());
            t.setPriority(priority);
            return t;
        } finally {
            lock.unlock();
        }
    }
}
